<template>
  <!--如果没有todo项就不展示底部栏-->
  <div class="todo-footer" v-show="total">
    <label>
      <!-- 通过绑定事件进行全选-->
      <!--<input type="checkbox" :checked="isAll" @change="checkAll"/>-->
      <!-- 通过v-model进行全选-->
      <input type="checkbox" v-model="isAll"/>
    </label>
    <span>
          <span>已完成{{ doneTotal }}</span> / 全部{{ total }}
        </span>
    <button class="btn btn-danger" @click="clearAll">清除已完成任务</button>
  </div>
</template>

<script>
export default {
  name: "MyFooter",
  props: ['todos', 'checkAllTodo', 'clearAllTodo'],
  computed: {
    doneTotal() {
      // pre是上一次调用的返回值，todo是数组中每个元素
      return this.todos.reduce((pre, todo) => {
        return pre + (todo.done ? 1 : 0);
      }, 0);
    },
    total() {
      return this.todos.length
    },
    // 计算属性允许套娃 可以通过完整形式将全选和状态合并
    isAll: {
      get() {
        return this.doneTotal === this.total && this.total > 0;
      },
      set(value) {
        this.checkAllTodo(value);
      }
    }
  },
  methods: {
    // checkAll(e) {
    //   this.checkAllTodo(e.target.checked);
    // }
    clearAll() {
      this.clearAllTodo();
    }
  }
}
</script>

<style scoped>
/*footer*/
.todo-footer {
  height: 40px;
  line-height: 40px;
  padding-left: 6px;
  margin-top: 5px;
}

.todo-footer label {
  display: inline-block;
  margin-right: 20px;
  cursor: pointer;
}

.todo-footer label input {
  position: relative;
  top: -1px;
  vertical-align: middle;
  margin-right: 5px;
}

.todo-footer button {
  float: right;
  margin-top: 5px;
}
</style>